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The K 3's gun design was nothing innovative, but the same cannot be said for the carriage. Rheinmetall placed a lot of emphasis on ease of assembly. It did not require a crane because it used electric winches, mounted on the carriage, to pull various parts through a system of inclined ramps, guide rails and runways. It also used the Rheinmetall's dual-recoil system, first seen on the 21 cm Mörser 18. The barrel recoiled normally in its cradle, but, in addition, the whole top carriage, which carried the barrel and its cradle, recoiled across the main part of the carriage. This system damped out the recoil forces and made for a very steady firing platform.

The K 3 was a gigantic weapon that was transported in six loads. These consisted of the firing platform, the carriage, the cradle, the barrel, the breech and an electric generator.

The Wehrmacht was not content with the gun's performance: "It was felt to be wasteful of time and manpower, the transport arrangements were cumbersome and the performance was not considered to be commensurate with the size of weapon."[5] These led to experiments by Krupp and Rheinmetall to extend the range. These included "pre-grooved" projectiles which showed no significant improvement, squeeze-bore, discarding sabot and even a smoothbore version. None of these reached beyond the experimental stage.

Gander, Terry and Chamberlain, Peter. Weapons of the Third Reich: An Encyclopedic Survey of All Small Arms, Artillery and Special Weapons of the German Land Forces 1939-1945. New York: Doubleday, 1979 ISBN 0-385-15090-3